The last rays of the dying sun flooded the cave with a low, orange light. The gathered men sat rapt, staring at a figure hunkered down in their midst.

He looked up, godlike, and stared slowly round the circle, making eye contact with each of them. His hands held flint rocks turning slowly over and over, ensuring total attention.

The larger of the stones was placed on the floor and anchored with a huge hand and locked elbow. He placed the other stone by his feet and butted small twigs, kindling and fur up against the first.

Clutching the hammer stone in his hand, he raised it in salute above his head and bellowed a guttural stream of power.

The whole cave followed his hand as it arced down and struck its counterpart with an eruption of flickering fireflies. They gasped and scrabbled to move back, scared, but at the same time unable to draw their eyes from the sight.

The hand was lifted again and fell faster, with more control. The crack echoed back and forth around the cave.

Shreds of wood burst into living flame, smoke curled upward and tinged the air with acrid flavours.

The men didn't move away this time. As one they leant forward and stared into the dancing heart of humanity's first step into the unknown.